Hydraulic circuit for operating multiple cylinders



March 9, 1965 w. GOVAN 3,172,261

HYDRAULIC CIRCUIT FOR OPERATING MULTIPLE CYLINDERS Filed April 27, 1962 2 Sheets-Sheet 1 INVENTOR. MLLIAM L. ovn v BY AI'I'OAPNEYS March 9,1965 w. L. GO VAN 3,172,261

HYDRAULIC CIRCUIT FOR OPERATING MULTIPLE CYLINDERS Filed April 27, 1962 2 Sheets-Sheet 2 INVENTOR. Mum; L 60 v4! BY 7 YA/W M United States Patent '0 3,172,261 HYDRAULIC CIRCUIT FOR OPERATING MULTIPLE CYLINDERS William L. Govan, Brighton, N.Y., assignor to Farrel Corporation, a corporation of Connecticut Filed Apr. 27, 1962, Ser. No. 190,555 14 Claims. (Cl. Gil -52) This invention pertains to a hydraulic circuit by which a single reversible variable delivery pump or a single pumping bank which includes at least one reversible variable delivery 'pump is used to control and operate a number of independent hydraulic cylinders.

The primary object of this invention is to achieve with practical economy the smooth, shock free operation of all the main hydraulic cylinders used on a high pressure extrusion press or other comparable piece of equipment and to give each cylinder the progressive deceleration and acceleration in either direction that allows it to be reversed considerably faster than can be safely accomplished by means of the conventional pump and valve circuits. Heretofore these operating advantages have been achieved only with the expensive and cumbersome duplication of a separate variable delivery pump for each cylinder.

Briefly, the best mode presently contemplated for practicing this invention includes a bank of several reversible variable delivery pumps and several reversible fixed delivery pumps connected to common headers. For the purposes of this specification,a reversible fixed delivery pump includes and particularly refers to the conventional expedient of a non-reversible fixed delivery pump combined with a four way valve by means ot which its output can be discharged into the headers in either direction or recirculated to the reservoir.

The headers can be connected or disconnected to each of the hydraulic cylinders to be controlled. In one application, for which this invention has been found particularly well suited, one cylinder operates the main ram of a high pressure extrusion press, a second operates the shear, a third controls the die-slide and a fourth the internal piercer.

The valves making the header-to-cylinder connections are operated in the moment between pump operations while the variable delivery pumps idle, and the four way directional valve associated with each fixed delivery pump is recirculating that ,pumps discharge to the reservoir.

The next press operation is performed, when one header has been connected to each side of the appropriate cylinder, by controlling the variable delivery pumps to begin output which initiates piston movement in the appropriate direction. As soon as this has been accomplished, the reversible fixed delivery pumps are engaged to augment the fluid delivery capacity as may be done without danger of shock once slack in the system has been taken up by delivery from the variable delivery pumps.

The operation is stopped by first idling the reversible fixed delivery pumps output to the reservoir, and by then slowing delivery from the variable delivery pumps until, when they have reached the idling position, the hydraulic piston and controlled mechanism are stopped. Because this can be done smoothly, it may be done rapidly.

The invention is described in more detail below with reference to the following drawings in which:

FIGURE 1 is" a schematic drawing of two reversible variable discharge pumps, two fixed delivery pumps and the associated hydraulic circuit to the headers;

FIGURE 2 is a schematic drawing of a pair of three way directional valves with two associated cylinders; another pair of three way directional valves with two associated cylinders and the associated hydraulic circuit.

FIGURE 3 is a schematic drawing of an alternative 3,172,261 te e M r: 9' 1 "ice construction of two of 'tlie d'irectionalvalves associated with the cylinders and circuitry of FIGURE 2; and

FIGURE 4 is a schematic drawing of an alternative construction of another two of the directional valves associated with the cylinders and circuitry of FIG. 2.

As shown in 1, the pumping bank includes a conventional servo operated stroke controlled reversible variable delivery pump 1 powered by motor 2. It is connected from two pump delivery ports by lines 3 and 4 to circulate hydraulic fluid between headers 5 and 6. The direction of circulationis determined by the setting of the pump stroke control. Another pump '7 of the same sort is similarly connected to the headers by lines 8 and 9. It is powered by motor 10 which also drivesa conventional fixed delivery pump 11. Pump 11 draws from the reservoir 12 through line 13 and delivers to line 14. Line 14 is connected to relief valve 15, that bypasses back to the reservoir at some predetermined maximum pressure, and to a four way directional valve 16. This solenoid controlled and pilot operated valve, in its right hand position, connects line 14 to line 17 and line 18 to the reservoin lnits left hand position, it connects line 14 to line 18 and line 17 to the reservoir. It connects line 14 back to the reservoir 12, a nd also to line 18', in its center position. Check valve 19 prevents flow from header 6 through line 18. A second fixed delivery pump 29 .powered by motor 21 is connected to headers 5 and d by circuitry which may be the same as that used for pump 11.

Conventional means are used to provide pilot pressure to the valve controls. Likewise, the necessary electrical control circuitry wines known to those who are skilled in this art in view of the disclosure made here. These circuits are therefore not expilicitly set forth.

As shown in FIGS. 1 and 2, the header 5 is connected by line 22 to solenoid actuated pilot operated three way valves 23 and 24 which permit it to be connected and disconnected from each of the four cylinders to be controlled. I

Valve 23 caps or blocks line 22 at the valve in its center position. In its right hand position, it connects line 22 to line 25 and the bottom of hydraulic cylinder 26 which may, for example, operate the die-slide of an extrusion press. In its left hand position, it connects line 22 to line 27 and the top of hydraulic cylinder 28 which may, for example, operate the shear of an extrusion press.

Valve 24 in its center position caps or blocks' line 22 at the valve. In its right hand position it connects line 22 to line 29 and the right side of hydraulic cylinder 30, which, may, forexample, operate th'e ram of an extrusion press. Ordinarily, the conventional side cylinders will be provided with a prefill valve addition to the main cylinder for the more r'a'pid retraction mammal positioning of the main rain. Valve 24', in its left hand position connects line 22- to' line 31 and the right side of hydraulic cylinder 32 which may, for example, be connected to po'v've'r' the piercer of an extrusion press. I

Header 6 is connected by line 33 to three-way pilot operated directional valves 3'4 and 35 which permit it to be connected to and disconnected from each of the four cylinders 26, 28', and 32 on the opposite side from that to which header 5 is connected or disconnected.

Valve 34' caps or blocks line 33 in its central position. Inits right hand position, it connects line 33' to line 33a and the top of the hydraulic cylinder 26. In its left hand position, it connects line 33 to line 36 and the bottom of hydraulic cylinder 28.

Valve caps or blocks line 33 at the valve in its central position. In its right hand position, it connects line 33 to line 37 and the left side of the cylinder 30. In its left hand position, it connects line 33 to line 38 and the left side of hydraulic cylinder 32 5 to one side and header 6 to the other side of the same cylinder. In other Words, valves 23 and 34 (as well as valves 24 and 35) will be operated together as a pair. For this reason, the pilot cylinders of one can be connected to those of the other and one solenoid control valve used to cause the pair to operate together in the same direction. This is shown in the portion of the pilot pressure lines included for the valves 23 and 34 by which the pilot cylinders of valve 23 are solenoid controlled and those of valve 24 are connected with them.

The basic circuit described is, however, equally appropriate for more sophisticated hydraulic circuits and in such installations it is sometimes advantageous to supply fluid from the pumping bank to only one side of a cylinder and thus to have the valves independently controlled in both directions, or in at least one direction, as is the case for valves 24 and 35 as they are shown in FIGURE 3.

Filter and cooling systems are provided conventionally.

The system described above operates as follows. Hydraulic cylinder 28 is used as an illustrative example. Before starting the valves are all centered. The pumping bank is actuated, with the variable discharge pumps 1 and 7 in idle and the fixed discharge pumps 11 and 2t) recirculating to the reservoir through their associated four way directional valves.

To operate a cylinder, 28 for example, valves 23 and 34 are shifted to their left hand positions as the solenoid pilot valve 39 is operated to admit pilot pressure from source 40 into the right hand pilot cylinders of those valves. The valves are thereby shifted under no load conditions.

As soon as the three way directional valves 23 and 34 are operated, the stroke control of variable delivery pumps 2 and 7 are operated to draw in fluid through lines 4 and 9, respectively, and deliver fluid through lines 3 and 8, respectively, to circulate fluid from header 6 to header 5. Pressure differential created between the headers is transmitted through the previously described connections to the piston of hydraulic cylinder 28 and causes it to move downwardly.

When this motion has begun, the solenoid control of valve 16 is operated to cause the left hand pilot cylinder 41 to throw that valve to its right hand position connecting line 14 to line 17 and allowing the fixed delivery pump 11 to deliver fluid to header 5 from reservoir 12. The directional valve controlling the flow from fixed delivery pump 20 may be operated simultaneously with the directional valve controlling the flow from pump 11 or with a slight time delay.

The power stroke of the piston of cylinder 28 may be evenly decelerated and stopped by first moving the directional valves for pumps 11 and 20 to their central positions so that the capacity of those pumps is removed from the powering system and simply recirculated to and from the reservoir 12, except for that transmitted to header 6 through line 18 to keep the system full of fluid. The stroke controls of the variable delivery pumps are then operated to reduce pump displacement and provide gradual braking. When the piston has stopped, the shift of pump displacement may be continued to retract the piston or the variable displacement pumps continued in idle While the valves 23 and 24 disconnect the cylinder from the pumping bank.

The valves 23, 24, 33 and 34 are shown as four-way valves made three-way by blocking off one port. Alternatively, they may be used variously as four way valves to provide additional control. FIGURE 3 shows valves 23a and 34:: connected to provide positive holding of the pistons of cylinders 26 and 28 from a low pressure source supplied through line 42. The cylinders can also be connected to an accumulator or shock alleviator. FIGURE 4 shows valves 24m and 35a connected to allow the piston of cylinder 30 to drift or float when the valves ar centered during a part of the operational cycle.

I claim:

1. A hydraulic circuit including a reversible variable delivery pump with pump delivery ports, a plurality of cylinders, a plurality of valves and means connecting a valve between each pump delivery port and the cylinders so that a first pump delivery port may be connected to any of said cylinders and disconnected from each of the other cylinders and a second pump delivery port may be independently connected to the opposite side of any of said cylinders and disconnected from each of the other cylinders whereby the reversible variable delivery pump may be used as the power source for operating and reversing a piston element in each of said cylinders and idled while said valves are moved to connect and disconnect said ports from said cylinders.

2. A hydraulic circuit including a reversible variable delivery pump with pump delivery ports, two cylinders, two directional valves, means connecting one of said valves between the pump and one of said cylinders in a first position and the other of said cylinders in a second position and means connecting another of said valves between the pump and the opposite side of one of said cylinders in a first position and the other of said cylinders in a second position and means whereby the reversible variable delivery pump may be used as the power source for operating and reversing a piston element in either of said cylinders and said pump may be idled while said directional valves are operated between said first and second positions.

3. A hydraulic circuit including a reversible variable delivery pump, with pump delivery ports, four cylinders, a plurality of directional valves and means connecting a directional valve between each pump delivery port and the cylinders so that a first pump delivery port may be connected to any of said cylinders and disconnected from each of the other cylinders and a second pump delivery port may be independently connected to the opposite side of any of said cylinders and disconnected from each of the other cylinders whereby the reversible variable delivery pump may be used as the power source for operating and reversing a piston element in each of said cylinders and idled while said valves are moved to connect and disconnect said ports from said cylinders.

4. A hydraulic circuit including a reversible variable delivery pump, with pump delivery ports, four cylinders, four directional valves and means connecting a directional valve between a first pump delivery port and two of said cylinders and another directional valve between said first pump delivery port and the other two of said cylinders whereby said first pump delivery port may be connected to any of said cylinders and disconnected from each of the other cylinders and means connecting another directional valve between a second pump delivery port and two of said cylinders and another directional valve between said second pump delivery port and the other two of said cylinders whereby said second pump delivery port may be connected to the opposite side of any of said cylinders and disconnected from each of the other cylinders whereby the reversible variable delivery pump may be used as the power source for operating and reversing a piston in each of said cylinders and idled while said valves are moved to connect and disconnect said ports from said cylinders.

5. The hydraulic circuit of claim 4, one or more other reversible variable delivery pumps and means connecting said one or more other pumps in parallel with the reversible variable delivery pump of claim 4 whereby said other pumps may be operated with the .pump of claim 4.

6. The hydraulic circuit of claim 3, one -or more fixed delivery pumps, means connecting said one or more fixed delivery pumps in parallel with the reversible variable discharge pump and means connecting one or more of said fixed delivery pumps to a reservoir whereby the delivery of said fixed delivery pump may be recirculated to the reservoir while said valves are moved to connect and disconnect said ports from said cylinders and whereby the delivery of said fixed delivery pumps augments the delivery of the variable delivery pump.

7. The hydraulic circuit of claim 4, one or more fixed delivery pumps, means connecting said one or more fixed delivery pump in parallel with the reversible variable discharge pump and connecting one or more of said fixed delivery pumps to a reservoir whereby the delivery of said one or more fixed delivery pumps may be recirculated to the reservoir While said valves are moved to connect and disconnect said ports from said cylinders and whereby the delivery of said one or more fixed delivery pumps auguments the delivery of the variable delivery pump.

8. The hydraulic circuit of claim 4, one or more fixed delivery pumps, means connecting said one or more fixed delivery pumps in parallel with the reversible variable discharge pump and to a reservoir whereby the delivery of said one or more fixed delivery pumps may be recirculated to the resevoir while said valves are moved to connect and disconnect said ports with said cylinders and whereby the delivery of the said one or more fixed delivery pumps may augment the delivery of the said variable delivery pump.

9. The method of operating two hydraulic cylinders of an extrusion press by a single pumping bank having at least one reversible variable delivery pump having pump delivery ports that comprises the steps of connecting said pumping bank to directional valves and said directional valves to said cylinders; idling said pump and, while said pump is idling, operating said valves to connect the pump delivery ports to a first one of said cylinders; operating said pump to power said first hydraulic cylinder in one direction and then in the other direction; again idling said pump and, while said pump is idling, operating said valves to disconnect the pump delivery ports from said first cylinder and to connect them to a second cylinder; and operating said pump to power said second cylinder in one direction and then in the other direction.

10. The method of operating a plurality of hydraulic cylinders of an extrusion press by a single pumping bank having at least one reversible variable delivery pump having pump delivery ports that comprises the steps of connecting said pumping bank to directional valves and said directional valves to said cylinders; idling said pump and, while said pump is idling, operating said valves to connect the pump delivery ports to a first one of said cylinders; operating said pump to power said first hydraulic cylinder in one direction and then in the other direction; again idling said pump and, while said pump is idling, operating said valves to disconnect the pump delivery ports from said first cylinder and to connect them to a second cylinder; and operating said pump to operate said second cylinder in one direction and then in the other direction.

11. A hydraulic circuit with a reservoir including a reversible variable delivery pump having pump delivery ports, a plurality of cylinders, a plurality of directional valves at least two of which are four-way directional valves, and means connecting directional valves between a first pump delivery port and said cylinders so that said cylinders can be connected and disconnected from said first delivery port and means connecting other directional valves betwen a second pump delivery port and said cylinders so that said cylinders can be connected and disconnected from said second delivery port and wherein at least one of said directional valves and at least one of said other directional valves are four-way directional Valves said means connecting said four-Way valves between the delivery ports, the opposite side of the same cylinder and the reservoir whereby the reversible variable deli-very pump may be used as the power source for operating and reversing a piston element in each of said cylinders and idled while said valves are moved to connect and disconnect said cylinders from said ports and whereby said same cylinder may be allowed to drift during a part of the operating cycle.

12. A hydraulic circuit including a reversible variable delivery pump having pump delivery ports, a separate low pressure power source, a plurality of cylinders, a plurality of directional valves, and means connecting a directional valve between a first pump delivery port and said cylinders so that each of said cylinders can be connected and disconnected from said first delivery port and means connecting other directional valves between a second pump delivery port and said cylinders so that each of said cylinders can be connected and disconnected from said second delivery port, at least one of said directional valves being a four-way directional valve and at least one of said other directional valves being a four-way directional valve, said connecting means connecting said fourway directional valves between said pump delivery ports, a low pressure power source, and the opposite sides of the same cylinder whereby the reversible variable delivery pump may be used as the power source for operating and reversing a piston element in each of said cylinders and idled while said valves are moved to connect and disconnect said cylinders from said ports and whereby said four-way valves may be operated to connect said same cylinder to said low pressure power source for positive holding of a piston element within said same cylinder during a portion of the operation cycle.

13. The method of operating two or more hydraulic cylinders which comprises the steps of connecting a first source of hydraulic fluid before the piston element of a first of said hydraulic cylinders, connecting another source of hydraulic fluid behind the piston element of a first of said hydraulic cylinders, controlling said sources of hydraulic fluid to supply fluid on one side of said piston element and receive it from the other side of said piston element so as to cause said piston element to move within the cylinder, and for then causing the rate of supply of hydraulic fluid to continually decrease until hydraulic fluid is being received from said one side of said piston element and for causing the rate of receipt of hydraulic fluid to decrease until hydraulic fluid is being supplied to said other side of said piston element so that the piston element is smoothly slowed and reversed in movement within said first of said hydraulic cylinders; further controlling said sources of hydraulic fluid to decrease and stop the supply and receipt of hydraulic fluid so as to stop said piston element within said first of said hydraulic cylinders; disconnecting said sources of hydraulic fluid from said first of said hydraulic cylinders; connecting said sources of hydraulic fluid to a second of said hydraulic cylinders, one of said sources being connected before a piston in said second of said hydraulic cylinders and the other of said sources being connected behind the piston in said second of said hydraulic cylinders; controlling said sources of hydraulic fluid to supply fluid to one side of said piston and to receive fluid in the other side of said piston so as to cause said piston to move within said second cylinder of said hydraulic cylinders; controlling said sources of hydraulic fluid so as to decrease the supply of fluid at one side of said piston and to decrease the receipt of fluid at the other side of said piston so as to stop the piston within said second of said hydraulic cylinders; and disconnecting said sources of hydraulic fluid from said second of said hydraulic cylinders.

14. A hydraulic circuit including a reversible variable a '7 '8 delivery pump having two punip delivery ports, a plupower source for operating and reversing each of said rality of two or more cylinders each having a piston Cylinders separately and n t elemeht, a plurality of directional control valves for connecting said reversible variable delivery pump to each of References Cited in the file of this Patent said cylinders separately and in turn, and means for oper- 5 UNITED STATES PATENTS I ating said valves and controlling said reversible variable 1 3 7 Smith 9, .1927 delivery pump so that said valves are operated when said 2,098,425 L d b 9 1937 pump is idling and so that said pump may be used as the 2,316,926 Willett Apr. 20, 1943 

1. A HYDRAULIC CIRCUIT INCLUDING A REVERSIBLE VARIABLEE DELIVERY PUMP WITH PUMP DELIVERY PORTS, A PLURALITY OF CYLINDERS, A PLURALITY OF VALVES AND MEANS CONNECTING A VALVE BETWEEN EACH PUMP DELIVERY PORT AND THE CYLINDERS SO THAT A FIRST PUMP DELIVERY PORT MAY BE CONNECTED TO ANY OF SAID CYLINDERS AND DISCONNECTED FROM EACH OF THE OTHER CYLINDERS AND A SECOND PUMP DELIVERY PORT MAY BE INDEPENENDTLY CONNECTED TO THE OPPOSITE SIDE OF ANY OF SAID CYLINDERS AND DISCONNECTED FROM EACH OF THE 